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I did a cool mod to my XTC un-boosted Blue & Red channels. The mod came from this guy's post on the Bogner forums. Apparently when you switch off the boost, a resistor and a capacitor (R66 and C224, in parallel) get connected to ground.
http://bognerampforum.informe.com/just-did-a-mod-to-my-101b-very-happy-with-it-dt2224.html
That C224 cap cuts out a lot of the high end from the unboosted sound. If you remove that cap, the unboosted sound on Blue and Red channels is brighter; the same sort of brightness as the boosted Blue and Red.
(Note: once you cut that C224 cap, it's very difficult to put it back in. Check that guy's post for a way to test this mod before you cut that C224 cap, to make sure you like it first.)
I did the test and really liked the brighter unboosted Blue and Red sound. So I designed a way to make the mod switchable.
I cut C224 off the board, then rigged a DPDT on/off/on and wired it to the ends of the R66 resistor. On one pole, I put a 1000 pF cap--the same value as the stock C224 cap. On the other pole I put a 91k resistor. I installed the switch in one of the unused holes for the buttons for the FX loop switches, right next to my Marvel mod board.
So the switch in one position puts the 1000 pF cap in parallel with R66, to give the stock sound. In the middle 'off' position, it puts nothing in parallel and so gives the same sound as with C224 cut--brighter unboosted. In the other position, it puts the 91k ohms resistor on the switch in parallel with R66 (100k ohms), which is ~47k ohms, which is the value that apparently the Splawn Quickrod uses in its unboosted setting. (Shout-out to Setneck for that idea!)
I also put 10 Meg resistors across the switch terminals to the cap, so the cap wouldn't cause popping when switched in and out.
I'm really happy with it. The no-C224 brighter unboosted sound sounds great. It's a little crunchier than the stock unboosted, with a nice brightness to the high-end. The stock sound is darker. It seems to have a bit more midrange to it, but I think that's just the midrange sounding more prominent because there's less highs there. The lower-gain unboosted sound, with the Splawn resistor value, is a nice lower-gain version of the brighter unboosted. It takes the gain down a small but noticeable amount, and clears up the sound with less saturation. A cool alternative.
I highly recommend the no-C224 brighter unboosted sound. It really removes the blanket effect from the unboosted sound. (Test it first, before you cut out the C224 cap.)
If you're a tweaker or you want to experiment, you can try out something with a switch like I did. I'm curious if there are different cap values that might make the resistor + cap sound a bit less dark, or maybe a different brand of cap, like the ones Setneck likes. (I used a Mallory 150, which he says sounds darker than his.)
Some pics:
http://bognerampforum.informe.com/just-did-a-mod-to-my-101b-very-happy-with-it-dt2224.html
That C224 cap cuts out a lot of the high end from the unboosted sound. If you remove that cap, the unboosted sound on Blue and Red channels is brighter; the same sort of brightness as the boosted Blue and Red.
(Note: once you cut that C224 cap, it's very difficult to put it back in. Check that guy's post for a way to test this mod before you cut that C224 cap, to make sure you like it first.)
I did the test and really liked the brighter unboosted Blue and Red sound. So I designed a way to make the mod switchable.
I cut C224 off the board, then rigged a DPDT on/off/on and wired it to the ends of the R66 resistor. On one pole, I put a 1000 pF cap--the same value as the stock C224 cap. On the other pole I put a 91k resistor. I installed the switch in one of the unused holes for the buttons for the FX loop switches, right next to my Marvel mod board.
So the switch in one position puts the 1000 pF cap in parallel with R66, to give the stock sound. In the middle 'off' position, it puts nothing in parallel and so gives the same sound as with C224 cut--brighter unboosted. In the other position, it puts the 91k ohms resistor on the switch in parallel with R66 (100k ohms), which is ~47k ohms, which is the value that apparently the Splawn Quickrod uses in its unboosted setting. (Shout-out to Setneck for that idea!)
I also put 10 Meg resistors across the switch terminals to the cap, so the cap wouldn't cause popping when switched in and out.
I'm really happy with it. The no-C224 brighter unboosted sound sounds great. It's a little crunchier than the stock unboosted, with a nice brightness to the high-end. The stock sound is darker. It seems to have a bit more midrange to it, but I think that's just the midrange sounding more prominent because there's less highs there. The lower-gain unboosted sound, with the Splawn resistor value, is a nice lower-gain version of the brighter unboosted. It takes the gain down a small but noticeable amount, and clears up the sound with less saturation. A cool alternative.
I highly recommend the no-C224 brighter unboosted sound. It really removes the blanket effect from the unboosted sound. (Test it first, before you cut out the C224 cap.)
If you're a tweaker or you want to experiment, you can try out something with a switch like I did. I'm curious if there are different cap values that might make the resistor + cap sound a bit less dark, or maybe a different brand of cap, like the ones Setneck likes. (I used a Mallory 150, which he says sounds darker than his.)
Some pics:
